Techopedia explains Platform Agnostic

If the platform agnostic term is used, the platform must be defined. When referring to a software product, platforms typically refer to common operating systems (OS), like MS Windows, Mac OS, and Linux.

In other cases, the term may be used to refer to products and services that work with print and digital environments, or platforms. For example, media outlets that deliver content via print and digital environments are platform agnostic.

In yet another context, the term refers to user choices. For example, users that are true believers of a given platform may refer to radically different platform users as platform agnostic.